* [Cluster-devel] [PATCH] GFS2: minor readability improvement in gfs2_mount() @ 2013-06-05 21:29 Alexey Khoroshilov 2013-06-06 9:24 ` Steven Whitehouse 0 siblings, 1 reply; 4+ messages in thread From: Alexey Khoroshilov @ 2013-06-05 21:29 UTC (permalink / raw) To: cluster-devel.redhat.com The patch makes usage pattern of IS_ERR-PTR_ERR more typical. Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru> --- fs/gfs2/ops_fstype.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c index 0262c19..0d30e8e 100644 --- a/fs/gfs2/ops_fstype.c +++ b/fs/gfs2/ops_fstype.c @@ -1313,9 +1313,10 @@ static struct dentry *gfs2_mount(struct file_system_type *fs_type, int flags, } s = sget(fs_type, test_gfs2_super, set_gfs2_super, flags, bdev); mutex_unlock(&bdev->bd_fsfreeze_mutex); - error = PTR_ERR(s); - if (IS_ERR(s)) + if (IS_ERR(s)) { + error = PTR_ERR(s); goto error_bdev; + } if (s->s_root) blkdev_put(bdev, mode); -- 1.8.1.2 ^ permalink raw reply related [flat|nested] 4+ messages in thread
* [Cluster-devel] [PATCH] GFS2: minor readability improvement in gfs2_mount() 2013-06-05 21:29 [Cluster-devel] [PATCH] GFS2: minor readability improvement in gfs2_mount() Alexey Khoroshilov @ 2013-06-06 9:24 ` Steven Whitehouse 2013-06-07 6:49 ` Alexey Khoroshilov 0 siblings, 1 reply; 4+ messages in thread From: Steven Whitehouse @ 2013-06-06 9:24 UTC (permalink / raw) To: cluster-devel.redhat.com Hi, On Thu, 2013-06-06 at 01:29 +0400, Alexey Khoroshilov wrote: > The patch makes usage pattern of IS_ERR-PTR_ERR more typical. > > Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru> > --- > fs/gfs2/ops_fstype.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c > index 0262c19..0d30e8e 100644 > --- a/fs/gfs2/ops_fstype.c > +++ b/fs/gfs2/ops_fstype.c > @@ -1313,9 +1313,10 @@ static struct dentry *gfs2_mount(struct file_system_type *fs_type, int flags, > } > s = sget(fs_type, test_gfs2_super, set_gfs2_super, flags, bdev); > mutex_unlock(&bdev->bd_fsfreeze_mutex); > - error = PTR_ERR(s); > - if (IS_ERR(s)) > + if (IS_ERR(s)) { > + error = PTR_ERR(s); > goto error_bdev; > + } I'm not sure what you are getting at here. Why add a jump into the fast path? Steve. > > if (s->s_root) > blkdev_put(bdev, mode); ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Cluster-devel] [PATCH] GFS2: minor readability improvement in gfs2_mount() 2013-06-06 9:24 ` Steven Whitehouse @ 2013-06-07 6:49 ` Alexey Khoroshilov 2013-06-10 11:04 ` Steven Whitehouse 0 siblings, 1 reply; 4+ messages in thread From: Alexey Khoroshilov @ 2013-06-07 6:49 UTC (permalink / raw) To: cluster-devel.redhat.com Hi Steve, On 06/06/2013 01:24 PM, Steven Whitehouse wrote: > Hi, > > On Thu, 2013-06-06 at 01:29 +0400, Alexey Khoroshilov wrote: >> The patch makes usage pattern of IS_ERR-PTR_ERR more typical. >> >> Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru> >> --- >> fs/gfs2/ops_fstype.c | 5 +++-- >> 1 file changed, 3 insertions(+), 2 deletions(-) >> >> diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c >> index 0262c19..0d30e8e 100644 >> --- a/fs/gfs2/ops_fstype.c >> +++ b/fs/gfs2/ops_fstype.c >> @@ -1313,9 +1313,10 @@ static struct dentry *gfs2_mount(struct file_system_type *fs_type, int flags, >> } >> s = sget(fs_type, test_gfs2_super, set_gfs2_super, flags, bdev); >> mutex_unlock(&bdev->bd_fsfreeze_mutex); >> - error = PTR_ERR(s); >> - if (IS_ERR(s)) >> + if (IS_ERR(s)) { >> + error = PTR_ERR(s); >> goto error_bdev; >> + } > I'm not sure what you are getting at here. Why add a jump into the fast > path? My experiments with gcc 4.7.3 on x86-64 do not show any difference in code generated with patch and without it. 227a: e8 00 00 00 00 callq 227f <gfs2_mount+0xb1> 227b: R_X86_64_PC32 sget-0x4 227f: 4c 89 f7 mov %r14,%rdi 2282: 49 89 c4 mov %rax,%r12 2285: e8 00 00 00 00 callq 228a <gfs2_mount+0xbc> 2286: R_X86_64_PC32 mutex_unlock-0x4 228a: 49 81 fc 00 f0 ff ff cmp $0xfffffffffffff000,%r12 2291: 0f 87 2a 01 00 00 ja 23c1 <gfs2_mount+0x1f3> 2297: 49 83 7c 24 60 00 cmpq $0x0,0x60(%r12) 229d: 74 0b je 22aa <gfs2_mount+0xdc> 229f: 44 89 ee mov %r13d,%esi 22a2: 48 89 df mov %rbx,%rdi 22a5: e8 00 00 00 00 callq 22aa <gfs2_mount+0xdc> 22a6: R_X86_64_PC32 blkdev_put-0x4 It looks like 'error = PTR_ERR(s);' assignment is just ignored because s and error share the same register %r12. So the only point of the patch is to improve readability. -- Best regards, Alexey ^ permalink raw reply [flat|nested] 4+ messages in thread
* [Cluster-devel] [PATCH] GFS2: minor readability improvement in gfs2_mount() 2013-06-07 6:49 ` Alexey Khoroshilov @ 2013-06-10 11:04 ` Steven Whitehouse 0 siblings, 0 replies; 4+ messages in thread From: Steven Whitehouse @ 2013-06-10 11:04 UTC (permalink / raw) To: cluster-devel.redhat.com Hi, On Fri, 2013-06-07 at 10:49 +0400, Alexey Khoroshilov wrote: > Hi Steve, > > On 06/06/2013 01:24 PM, Steven Whitehouse wrote: > > Hi, > > > > On Thu, 2013-06-06 at 01:29 +0400, Alexey Khoroshilov wrote: > >> The patch makes usage pattern of IS_ERR-PTR_ERR more typical. > >> > >> Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru> > >> --- > >> fs/gfs2/ops_fstype.c | 5 +++-- > >> 1 file changed, 3 insertions(+), 2 deletions(-) > >> > >> diff --git a/fs/gfs2/ops_fstype.c b/fs/gfs2/ops_fstype.c > >> index 0262c19..0d30e8e 100644 > >> --- a/fs/gfs2/ops_fstype.c > >> +++ b/fs/gfs2/ops_fstype.c > >> @@ -1313,9 +1313,10 @@ static struct dentry *gfs2_mount(struct file_system_type *fs_type, int flags, > >> } > >> s = sget(fs_type, test_gfs2_super, set_gfs2_super, flags, bdev); > >> mutex_unlock(&bdev->bd_fsfreeze_mutex); > >> - error = PTR_ERR(s); > >> - if (IS_ERR(s)) > >> + if (IS_ERR(s)) { > >> + error = PTR_ERR(s); > >> goto error_bdev; > >> + } > > I'm not sure what you are getting at here. Why add a jump into the fast > > path? > My experiments with gcc 4.7.3 on x86-64 do not show any difference in > code generated with patch and without it. > 227a: e8 00 00 00 00 callq 227f <gfs2_mount+0xb1> > 227b: R_X86_64_PC32 sget-0x4 > 227f: 4c 89 f7 mov %r14,%rdi > 2282: 49 89 c4 mov %rax,%r12 > 2285: e8 00 00 00 00 callq 228a <gfs2_mount+0xbc> > 2286: R_X86_64_PC32 mutex_unlock-0x4 > 228a: 49 81 fc 00 f0 ff ff cmp $0xfffffffffffff000,%r12 > 2291: 0f 87 2a 01 00 00 ja 23c1 <gfs2_mount+0x1f3> > 2297: 49 83 7c 24 60 00 cmpq $0x0,0x60(%r12) > 229d: 74 0b je 22aa <gfs2_mount+0xdc> > 229f: 44 89 ee mov %r13d,%esi > 22a2: 48 89 df mov %rbx,%rdi > 22a5: e8 00 00 00 00 callq 22aa <gfs2_mount+0xdc> > 22a6: R_X86_64_PC32 blkdev_put-0x4 > > It looks like 'error = PTR_ERR(s);' assignment is just ignored because s and error share the same register %r12. > > So the only point of the patch is to improve readability. > Hmm, ok. I'm still not convinced that it does really improve readability in this case I'm afraid, so I'm not going to apply this one, Steve. > -- > Best regards, > Alexey ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2013-06-10 11:04 UTC | newest] Thread overview: 4+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2013-06-05 21:29 [Cluster-devel] [PATCH] GFS2: minor readability improvement in gfs2_mount() Alexey Khoroshilov 2013-06-06 9:24 ` Steven Whitehouse 2013-06-07 6:49 ` Alexey Khoroshilov 2013-06-10 11:04 ` Steven Whitehouse
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).